Question: 2 glue sticks cost $3.92. Which equation would help determine the cost of 9 glue sticks?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 2 glue sticks cost $3.92 as a proportion: $\dfrac{2}{\$3.92}$ Let $x$ represent the unknown cost of 9 glue sticks. Since 9 glue sticks cost $x$ , we have the following proportion: $\dfrac{9}{x}$ The cost changes along with the number of glue sticks purchased, and so the two proportions are equivalent. $\dfrac{2}{\$3.92} = \dfrac{9}{x}$